- The definition of zealous is having passionate energy for a belief or purpose.
An example of zealous is a preacher in an energetic church.
Origin of zealousMedieval Latin zelosus ; from Ecclesiastical Late Latin zelus: see zeal
(comparative more zealous, superlative most zealous)
From Ancient Greek Î¶Î®Î»Î¿Ï‚ (zÄ“los, â€œzeal, jealousyâ€), from Î¶Î·Î»ÏŒÏ‰ (zÄ“loÅ, â€œto emulate, to be jealousâ€).